Layal K. Jambi

A small field of view camera for hybrid gamma and optical imaging

The development of compact low profile gamma-ray detectors has allowed the production of small field of view, hand held imaging devices for use at the patient bedside and in operating theatres. The combination of an optical and a gamma camera, in a co-aligned configuration, offers high spatial resolution multi-modal imaging giving a superimposed scintigraphic and optical image. This innovative introduction of hybrid imaging offers new possibilities for assisting surgeons in localising the site of uptake in procedures such as sentinel node detection. Recent improvements to the camera system along with results of phantom and clinical imaging are reported.

Lymphoscintigraphic imaging study for quantitative evaluation of a small field of view (SFOV) gamma camera

The Hybrid Compact Gamma Camera (HCGC) is a portable optical-gamma hybrid imager designed for intraoperative medical imaging, particularly for sentinel lymph node biopsy procedures. To investigate the capability of the HCGC in lymphatic system imaging, two lymphoscintigraphic phantoms have been designed and constructed. These phantoms allowed quantitative assessment and evaluation of the HCGC for lymphatic vessel (LV) and sentinel lymph node (SLN) detection. Fused optical and gamma images showed good alignment of the two modalities allowing localisation of activity within the LV and the SLN. At an imaging distance of 10 cm, the spatial resolution of the HCGC during the detection process of the simulated LV was not degraded at a separation of more than 1.5 cm (variation <5%) from the injection site (IS). Even in the presence of the IS the targeted LV was detectable with an acquisition time of less than 2 minutes. The HCGC could detect SLNs containing different radioactivity concentrations (ranging between 1:20 to 1:100 SLN to IS activity ratios) and under various scattering thicknesses (ranging between 5 mm to 30 mm) with high contrast-to-noise ratio (CNR) values (ranging between 11.6 and 110.8). The HCGC can detect the simulated SLNs at various IS to SLN distances, different IS to SLN activity ratios and through varied scattering medium thicknesses. The HCGC provided an accurate physical localisation of radiopharmaceutical uptake in the simulated SLN. These characteristics of the HCGC reflect its suitability for utilisation in lymphatic vessel drainage imaging and SLN imaging in patients in different critical clinical situations such as interventional and surgical procedures.

A Multimodality Hybrid Gamma-Optical Camera for Intraoperative Imaging

The development of low profile gamma-ray detectors has encouraged the production of small field of view (SFOV) hand-held imaging devices for use at the patient bedside and in operating theatres. Early development of these SFOV cameras was focussed on a single modality—gamma ray imaging. Recently, a hybrid system—gamma plus optical imaging—has been developed. This combination of optical and gamma cameras enables high spatial resolution multi-modal imaging, giving a superimposed scintigraphic and optical image. Hybrid imaging offers new possibilities for assisting clinicians and surgeons in localising the site of uptake in procedures such as sentinel node detection. The hybrid camera concept can be extended to a multimodal detector design which can offer stereoscopic images, depth estimation of gamma-emitting sources, and simultaneous gamma and fluorescence imaging. Recent improvements to the hybrid camera have been used to produce dual-modality images in both laboratory simulations and in the clinic. Hybrid imaging of a patient who underwent thyroid scintigraphy is reported. In addition, we present data which shows that the hybrid camera concept can be extended to estimate the position and depth of radionuclide distribution within an object and also report the first combined gamma and Near-Infrared (NIR) fluorescence images.

A comparison of CsI:Tl and GOS in a scintillator-CCD detector for nuclear medicine imaging

A number of portable gamma cameras for medical imaging use scintillator-CCD based detectors. This paper compares the performance of a scintillator-CCD based portable gamma camera with either a columnar CsI:Tl or a pixelated GOS scintillator installed. The CsI:Tl scintillator has a sensitivity of 40% at 140.5 keV compared to 54% with the GOS scintillator. The intrinsic spatial resolution of the pixelated GOS detector was 1.09 mm, over 4 times poorer than for CsI:Tl. Count rate capability was also found to be significantly lower when the GOS scintillator was used. The uniformity was comparable for both scintillators.

Evaluation of XRI-UNO CdTe detector for nuclear medical imaging

Over the last two decades advances in semiconductor detector technology have reached the point where they are sufficiently sensitive to become an alternative to scintillators for high energy gamma ray detection for application in fields such as medical imaging. This paper assessed the Cadmium-Telluride (CdTe) XRI-UNO semiconductor detector produced by X-RAY Imatek for photon energies of interest in nuclear imaging. The XRI-UNO detector was found to have an intrinsic spatial resolution of <0.5mm and a high incident count rate capability up to at least 1680cps. The system spatial resolution, uniformity and sensitivity characteristics are also reported.

A novel compact small field of view hybrid gamma camera: first clinical results

Introduction Hybrid imaging has proven to be a major innovation in nuclear medicine, allowing the fusion of functional information with anatomical detail. In the past, the use of hybrid imaging such as PET-CT, PET-MRI and SPECT-CT has been of great clinical benefit; however, these scanners are relatively large and bulky. We have developed and investigated the clinical application of a compact small field of view hybrid gamma camera (HGC) that is suitable for small-organ imaging at the patient bedside. Patients and methods The HGC – consisting of a CsI(Tl) scintillation crystal coupled to an electron-multiplying charge-coupled device and an optical camera – was used in this study. Eligible patients attending the nuclear medicine clinic at Queen’s Medical Centre, Nottingham University Hospitals NHS Trust, Nottingham, UK, were invited to take part in this study. Following the standard injection of either a 99mTc-labelled or 123I-labelled radiopharmaceutical, images of the patient were acquired using the HGC and presented in a fused optical-gamma display. Results There were 24 patients enrolled in the study (age range between 30 and 83 years, mean: 58.6 years), images of 18 of whom were successfully acquired. These included patients who were undergoing bone, thyroid, lacrimal drainage, DaTscan and lymphatic imaging. In general, the small field of view system was well suited to small-organ imaging. The uptake could be clearly seen in relation to the patient surface anatomy and showed particular promise for lymphatic, thyroid and lacrimal drainage studies. Conclusion This pilot study has demonstrated the first clinical results of hybrid optical-gamma imaging in patients. The use of this system has raised new possibilities for small-organ imaging, in which the localization of radiopharmaceutical uptake can be presented in an anatomical context using optical imaging. The compact nature of the hybrid system offers the potential for bedside investigations and intraoperative use.

Quantitative investigation of a novel small field of view hybrid gamma camera (HGC) capability for sentinel lymph node detection

Objective: The hybrid gamma camera (HGC) has been developed to enhance the localization of radiopharmaceutical uptake in targeted tissues during surgical procedures such as sentinel lymph node (SLN) biopsy. To assess the capability of the HGC, a lymph node contrast (LNC) phantom was constructed to simulate medical scenarios of varying radioactivity concentrations and SLN size. Methods: The phantom was constructed using two clear acrylic glass plates. The SLNs were simulated by circular wells of diameters ranging from 10 to 2.5 mm (16 wells in total) in 1 plate. The second plate contains four larger rectangular wells to simulate tissue background activity surrounding the SLNs. The activity used to simulate each SLN ranged between 4 and 0.025 MBq. The activity concentration ratio between the background and the activity injected in the SLNs was 1 : 10. The LNC phantom was placed at different depths of scattering material ranging between 5 and 40 mm. The collimator-to-source distance was 120 mm. Image acquisition times ranged from 60 to 240 s. Results: Contrast-to-noise ratio analysis and full-width-at-half-maximum (FWHM) measurements of the simulated SLNs were carried out for the images obtained. Over the range of activities used, the HGC detected between 87.5 and 100% of the SLNs through 20 mm of scattering material and 75–93.75% of the SLNs through 40 mm of scattering material. The FWHM of the detected SLNs ranged between 11.93 and 14.70 mm. Conclusion: The HGC is capable of detecting low accumulation of activity in small SLNs, indicating its usefulness as an intraoperative imaging system during surgical SLN procedures. Advances in knowledge: This study investigates the capability of a novel small-field-of-view (SFOV) HGC to detect low activity uptake in small SLNs. The phantom and procedure described are inexpensive and could be easily replicated and applied to any SFOV camera, to provide a comparison between systems with clinically relevant results.

A novel small field of view hybrid gamma camera for scintigraphic imaging (Conference Presentation)

A novel small field of view Hybrid Gamma Camera (HGC) has been developed to facilitate the process of localizing radiopharmaceutical uptake during surgical procedures. The HGC is a scintillator-based detector consisting of an electron multiplying charge-coupled device coupled to a columnar scintillator (CsI[Tl]). This enables fusion scintigraphic and optical images offering new possibilities for assisting clinicians and surgeons in localising the site of uptake in a number of surgical procedures. This technology also offers bedside imaging for small organs in procedures such as thyroid scintigraphy. In this study, prototype anthropomorphic phantoms have been used to study the capability of the HGC. Images were acquired using a range of bespoke anthropomorphic phantoms. The gamma and hybrid optical images were acquired for the simulated sentinel lymph nodes and thyroid gland. The gamma images produced varied in terms of spatial resolution and detectability, however utilizing pinhole collimators of difference diameters (0.5 and 1.0mm) imaging was enhanced meeting the needs of small field gamma imaging. The hybrid images obtained demonstrated that the HGC is ideally suited for small organ imaging demonstrating good potential in clinical procedures, such as thyroid scintigraphy, when using acquisition times similar to those for conventional gamma imaging. Moreover, clinical scintigraphic images, from patients attending the nuclear medicine clinic, were acquired using the HGC and compared to images from a standard gamma camera. The results of our first clinical feasibility study using the HGC will be presented.

Comparison of columnar and pixelated scintillators for small field of view hybrid gamma camera imaging

For intraoperative medical imaging, the development of small field of view (SFOV) hybrid gamma cameras is an expanding area of research. The performance characteristics of a new innovation combining both gamma and optical imaging in a co-aligned configuration, the Hybrid Gamma Camera (HGC) have been evaluated and compared. In this study the HGC was fitted with either 1500 μm thick columnar CsI:TI or 1500 μm thick pixelated GOS scintillators. The columnar CsI:TI scintillator has an intrinsic spatial resolution of 230 μm compared to 1090 μm for the pixelated GOS scintillator. The sensitivity at 140.5 keV of the CsI:TI was 40 %, however, for the GOS it was 54 %. The intrinsic spatial uniformity was comparable for both CsI:TI and GOS scintillators. There was a significant difference between the CsI:TI and GOS scintillators for count rate capability which was lower when using a GOS scintillator.